Starting engine with hydraulic drive and means to preheat main engine



July 5, 1960 2,943,617

A. A. ZUHN STARTING ENGINE WITH HYDRAULIC DRIVE AND MEANS T0 PREHEAT MAIN ENGINE Filed Feb. 4' 1959 INVENTOR. ART/1'06 A Zu/m/ 4...! y 7 TORNL'YS United States Patent "cc STARTING ENGINE WITH HYDRAULIC DRIVE AND MEANS TO PREHEAT MAIN ENGINE Arthur A. Zuhn, East Peoria, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill., a corporation of California Filed Feb. 4, 19 59, Ser. No. 791,157

1 Claim. (Cl. 123-179) This invention relates to the starting of engines and particularly to starting engines when they are cold.

It is common practice to utilize a small internal combustion engine for motoring a large one to induce starting. The small engine is usually a gasoline engine which is relatively easily started and it is connected by a pinion and ring gear with the larger engine which is most often a compression ignition engine of the diesel type notoriously difficult to start particularly when it is cold.

It is also well known to utilize heat from the starting engine through direct contact from its cooling water and from its exhaust to heat the main engine to a degree where it is capable of being started.

It has now become a practice of some engine manufacturers to employ a hydraulic torque converter or fluid coupling between the starting engine and the engine to be started.

It is the object of the present invention to provide in combination with a starting engine, a main engine and a hydraulic drive therebetween, a means to utilize fluid heated in the operation of said drive to heat the main engine While also dissipating heat from the hydraulic drive.

A further object is to provide means for automatically circulating fluid between the hydraulic drive and the main engine when the main engine is too cold to be turned over or motored by the starting engine and automatically to discontinue the circulation and motor the main engine when it attains the required temperature.

Further objects and advantages of the invention will be made apparent in the following specification wherein reference is made to the accompanying drawing in which the invention is illustrated.

In the drawing a typical combustion engine is generally indicated at as being provided with an auxiliary starting system such as a gasoline starting engine shown at 12 connected to a ring gear 15 on the flywheel of the main engine through a conventional pinion 16 which is adapted to be driven by engine 12 through a hydraulic drive shown at 18. The hydraulic drive may be of any conventional type capable of using a fluid such as lubricating oil of the kind used in the main engine and in which the fluid may be circulated through the drive in operation.

In practice, the starting engine 12 is started independently of the main engine and drives the hydraulic means 18 and also a fluid supply pump 23 thereon, the suction side of which is connected as by a line 24 with the oil Patented July 5, 1960 sump of the main engine within its pan illustrated at 26.

The pressure side of the pump 23 is connected as by a line 25 to the hydraulic drive 18 to supply the necessary hydraulic fluid thereto. When the engine 10 is cold, as after a long period of shutdown, cranking forces are required in excess of the capacity of the hydraulic drive mechanism 18 and the torque required for motoring the main engine may even be so great as to stall the starting engine pinion.

In accordance with the present invention, a return line shown at 29 is connected between the hydraulic drive mechanism 18 and the sump of the main engine 10 and a check valve 28 is disposed in this line, the check valve being resiliently held in closed position as by a spring as indicated in the drawing.

In operation, when the starting engine is started and the pinion 16 engaged with the ring gear 15, if the torque required for motoring the main engine is sufl'iciently great to stall the pinion, the high pressure resulting in the hydraulic drive mechanism 18 will be relieved through the check valve and returned through the line 29 to the sump of the main engine. Since the oil acquires heat due to friction in being passed through the hydraulic mechanism and since new cold oil is continuously being pumped into the hydraulic mechanism, excessive heat in this mechanism is dissipated and is added to the body of oil in the sump of the main engine. The tension of the spring on the check valve 28 is such as to relieve this pressure before the starting engine is stalled and consequently the starting engine will continue to operate and oil will continue to be circulated cooling the hydraulic mechanism and gradually heating the oil in the main engine contributing considerably to any other heat which it receives as a result of the operation of the starting engine.

When, due to increasing the temperature of the main engine, the torque required to motor it is reduced to the capacity of the starting engine and the hydraulic drive mechanism at the pressure established by check valve 28, the main engine will automatically start to motor and as its temperature increases will attain the speed at which combustion takes place within its own cylinders and starting will have been accomplished. At this time the starter pinion is automatically disengaged through the conventional mechanism employed for this purpose and the starting engine can be shut down.

it claim:

In combination with a main internal combustion engine, a starting engine therefor, and a hydraulic drive means between said engines, pump means for Withdrawing lubricating oil from the main engine to supply the hydraulic drive means, a return line from the hydraulic drive means to the main engine, whereby heat in the drive means will be dissipated and acquired by the main engine prior to starting thereof, and a check valve in said return line to close said line when less than a predetermined torque is required to motor, the main engine.

References Cited in the file of this patent FOREIGN PATENTS 765,764 Germany Feb. 9, 1953 

